Numerical investigation of bidirectionally tunable, nanometer-precise, and compact tweezers for screening gold nanoparticles

Abstract

Unique optical and chemical properties of gold nanoparticles (NPs), besides their compatibility with biological entities, have led to the emergence of gold NPs as ideal candidates for biomedical applications if their size can be controlled with nanometer resolution. Taking advantage of (i) enhanced and confined dual wavelength counterpropagating leaky surface plasmons, (ii) different chemical potential dependencies of graphene’s optical transitions for different incident wavelengths, and (iii) different and intensive size dependencies of the extinction efficiency of plasmonic gold NPs for different incident wavelengths, (i) efficient, (ii) tunable, and (iii) bidirectional tweezers with nanometer precision have been proposed. At low laser intensities, but at the cost of speed, the proposed setup can be relatively compact due to the realized bidirectional feature that cannot be achieved in conventional unidirectional tweezers. Finite-difference time-domain calculations show that the proposed setup benefits from a dynamical fast tuning of the screening radius ( ∼ 1.73 µ s / m m 2 ), high bidirectional sorting sensitivity ( ∼ 14 n m / m e V ), and low tuning voltage ( ∼ 0.35 V ). The ability to integrate miniaturized parallel systems with individual operation on a single chip is another potential capability of the proposed system, which makes it a promising candidate for future lab-on-a-chip devices.